import java.lang.*;
import java.io.*;

/**
  * Object superclass
  *
  * Each type of object must extend and implement this class.
  * @author Anthony Steed
  * @version 1.0
  */

public abstract class Object {
  /** 
    * Holds the material of this object
    */
  public Material SurfaceMaterial;
  
  /**
    * Find the intersection of an object and a given ray.
    *
    * The return value is positive is the intersection is found and
    * this value gives the distance along the ray. Negative values
    * imply that the intersection was either not successful or the
    * intersection point was before the origin. This value can be used
    * with the pointAt method of the Ray class (@see Ray#pointAt)
    *
    * @param ray the ray to intersect with 
    * @return a <code>double</code> value that gives the distance
    * along the ray.
    */
  abstract public double intersect(Ray ray);

  
  /**
    * Find the normal of an object at the given point on its surface.
    * @param pt the surface point to find the normal at
    * @return a vector that contains the required normal
    */

  abstract public Vector normal(Point pt);

  /**
    * Read the object from the given source
    * @param is the source to read from
    * @exception java.io.IOException
    * if the light can not be read
    * @exception java.io.NumberFormatException
    * if there a number format error is encountered
    */
  abstract public void read(SceneReader is) 
    throws IOException, NumberFormatException;

  
  /**
    * Write the object to the given destination
    * @param os  the destination to write to
    * @exception java.io.IOException
    * if the write fails.
    */
  abstract public void write(SceneWriter os) throws IOException;

  /** 
    * Print a human readable version of the object definition to the
    * given destination
    * @param os  the destination to write to
    * @exception java.io.IOException
    * if the write fails.
    */
  abstract public void print(SceneWriter os) throws IOException;
}